import java.util.*;
import java.math.*;

public class pre {
    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
		String str = s.next();
		int t=0,r=0,e=0;
		
		for(int i=0; i<str.length();i++){
			if(str.charAt(i)=='t')
				t++;
			else if(str.charAt(i)=='r')
				r++;
			else if(str.charAt(i)=='e')
				e++;
		}
		
		int count=0;
		
		while(t>0 || r>0 || e>0){
			t--;
			r--;
			e-=2;
			count++;
		}
		
		System.out.println(count);
    }
}